1. Field of the Invention
The present invention relates to a hydraulic system that includes a pump for feeding hydraulic fluid from a pump inlet side to a pump outlet side, wherein a pressure accumulator is disposed on the outlet side as well as a control valve for use in such a hydraulic system.
2. Description of the Related Art
In order to provide hydraulic pressure in a motor vehicle, there are three basic known approaches: a hydraulic pump directly driven by an internal combustion engine; a hydraulic pump driven by an electric motor . Either a hydraulic pressure accumulator is filled by the hydraulic pump, or the hydraulic pump-is regulated in accordance with the respective requirements. Hydraulic drives are used in vehicles in many ways, e.g., for operating a variable speed drive unit of a continuously variable transmission, for shifting an automatic transmission, or the like. Such hydraulic subsystems are subsequently designated as hydraulic components, as opposed to the pressure generation unit, which constitutes an independent hydraulic system in the sense of the present invention.
In particular, when the pump of the hydraulic system is directly driven by a crankshaft of an internal combustion engine, the problem arises that a comparatively high shaft power is consumed by the pump, even when hydraulic fluid is not utilized by a hydraulic component.
It is therefore an object of the present invention to provide a hydraulic system whose shaft power for driving the pump is reduced, in particular in operating phases in which no volumetric flow or only a very small volumetric flow is received by a hydraulic component.